Method and apparatus for biological activation waste water treatment

ABSTRACT

Biological activation waste water purification method is disclosed, wherein the waste water is biologically purified in an activation process. Activated sludge is pumped into a circulation circuit comprising a flow channel and at least one distribution channel. Raw waste water is added to the activated sludge to form an activation mixture which is gradually denitrified as it flows through the circulation circuit. The activation mixture is aerated so as to suspend the activated sludge in the mixture while gradually saturating the activation mixture with oxygen so as to change the denitrifying of the mixture to the nitrifying of a mixture as the mixture flows through the circulation circuit. The activation mixture then flows to a fluidized bed filter where it is separated into purified water and activated sludge. The apparatus for biological activation waste water purification comprises a tank with at least one basic module on the bottom of the tank and spaced from the walls of the tank and defining a flow channel about the module. The module has a pair of partition walls which define a pair of separation spaces with the side walls of the basic module and also define a distribution channel which communicates with the flow channel. The partitions also have at least one opening communicating with the separation space and the distribution channel. Aeration members are located in the tank between the basic module and the walls of the tank and between the pair of partitions.

The present invention relates to a method for biological activationwaste water purification, wherein the waste water is purified in anactivation process, during which a nitrification occurs. The presentinvention also relates to an apparatus for realizing said method, whichcomprises in a common tank an activation space and upwards extendinglongitudinal separation spaces, from which the outlets for purifiedwater are led out, where each separation space is defined by thepartitions and the faces and communicates with the activation space atone longitudinal side.

BACKGROUND OF THE INVENTION

An effective protection of the surface water, including seas, againsteutrophication requires the utmost effectivity of removal of macrobiogenelements as nitrogen and phosphorus, the presence of which in the wastewater is the main cause for the eutrophication phenomenon. That's whyall systems for waste water purification have to consider this call forremoving the nitrogen and phosphorus.

Hitherto known and used systems for waste water purification withsimultaneous reduction of the nitrogen content are orientated tobiological processes, which seem to be the most economical ones. Allsaid processes require first a conversion of the oxidable nitrogenforms, i.e. the ammoniacal and organic nitrogen, through thenitrification processes to the nitrate form. Then the nitrate reductionthrough the denitrification processes to the gaseous nitrogen follows.

The nitrification requires a presence of the nitrification bacteria inthe activated sludge, which requires a sufficient sludge age,practically the entire nitrification being attained at the sludge age of30 days, which corresponds to the sludge load 0.12 kg of biologicaloxygen demand in five days per one kilogramme of volatile suspendedsolids of the activated sludge multiplied by the number of the days,further called as kg BOD₅ /kg VSS.d In addition, the nitrificationprocesses require a sufficient concentration of the dissolved oxygen, asa rule over two milligram of the oxygen per one liter of theliquid--further called as 2 mg O₂ /l. The following denitrification isthen in progress while there is a shortage of dissolved oxygen in theliquid, whereby the microorganisms get the necessary oxygen throughnitrate reduction.

The prior art knows three essential alternatives for the solution of thesystem for complex biological water purification with a simultaneousnitrification and denitrification.

The first alternative is an intermittent denitrification. In thissolution the nitrification and denitrification phases of the activationpurification periodically alternate through an intermittent aerating.The disadvantage of this solution is a reduced effectiveness of theintermittent process compared with the continual one, complicatedregulation of the process and also ceasing of the suspension of theactivated sludge during the aerating interruption.

Another alternative is a preceding denitrification. In this solution isa separated denitrification in the form of a perfectly mixed tank withan intense mixing supply realized before the aerated activation. Duringthe preceding denitrification process the waste water is carried outtogether with the activation mixture recirculated from the aeratedactivation. The disadvantage of the preceding denitrification is thenecessity to create a separated denitrification activation space with anindependent source of movement of the activation mixture in order tosecure an activated sludge suspendation.

A necessary volume of denitrification activation depends on waste waterquality and process parameters and therefore it changes itself withrespect to time and locality. In order to secure purification in a goodquality the fixed volume has to have the size sufficient for an extremecase and therefore is usually overdimensioned.

Another disadvantage is that a part of the surface of thedenitrification space is not utilized for the activated sludgeseparation, the not utilized part being up to 25% of the surface in areactor in a municipal waste water treatment plant.

An example of solution with separated denitrification space andseparated aerated activation space represents e.g. patent specificationsCA - A 1 155 976 and EP - A 0 367 756. In the first mentioned patentspecification an embodiment is disclosed where a single centrallylocated anoxide zone and two aerobic zones are designed, located at thetwo end sides of reaction tank, each aerobic zone being divided by solidwall partition means into a downflow aeration zone and an upflowfluidized bed zone. This solution has the disadvantages of fixedfunctional volumes mentioned above.

In the second mentioned patent specification an inner denitrificationspace and outer nitrification space are disclosed and the solution isdirected to regulation of circulation flow by means of changing thecross section of passage between those spaces. The disadvantages of thefixed functional volumes are there inherent, too.

The third known alternative of denitrification during the biologicalwater purification is a denitrification in a circulation circuit of atype with oxidization ditches and carousel systems. In this case thefunctions of aeration and mixing of the waste water with the activationmixture are fused with supplying the movement of the activation mixturein the purifying system, in one system in the form of a mechanicaerator. With a flow of the activation mixture through the circulationcircuit saturation of the activation mixture with the dissolved oxygenoccurs, through that a nitrification occurs and through a gradualconsumption of the oxygen by the oxidation processes of thebiodegradation and nitrification the oxygen content in the activationmixture is decreasing, so that at the end of the circulation circuit thedenitrification process is performed with an oxygen lack.

Said technical solution of the denitrification shows many disadvantages.Mechanical aeration needs flat, not deep tanks, which need a largeconstruction place. The surface of the tank is not used for separationof the activated sludge, the consequence of which is the requirement ofcompleting of the activation apparatus by an independent separationequipment, which further increases the construction place size necessaryand therefore the investment costs. Sideline independent separation witha forced recirculation through the separated sludge settling is not veryeffective and causes a low operating concentration in the activationpart. The need of a low loading of the activated sludge with the sludgeage of 30 days results in large volumes of the activation space.

A considerable disadvantage of the circulation circuits is also a highsludge index in the activated sludge resulting from an insufficientreleasing of the gaseous nitrogen bubbles sticking to activated sludgeparticles during the the denitrification, which results in a significantlowering of the apparatus capacity.

Another disadvantage of the fusing of three functions, i.e. aeration,supplying of movement of the activation mixture and mixing the wastewater with the activation mixture, is that said fusing causes loweringof the denitrification effectiveness in the waste water with a highercontent of the nitrogen pollution, which results from a lack of a carbonsupply needed for denitrification processes in the denitrification part.To provide a sufficiently effective nitrification and denitrification itis therefore necessary to combine said apparatus with an intermittentaeration of the activation mixture with all the negative effects on theintermittent process.

The above mentioned known solutions of the denitrification showdisadvantages for both new waste water purification plant constructionand reconstruction of existing classical waste water purificationplants, which no more respond to the increased demands for a purifiedwater quality considering the eutrophication elements. There is a lot ofmunicipal waste water purification plants built in the fully developedindustrial countries which already need to be intensified orreconstructed. Hitherto existing solutions of denitrification are notsuitable for it, because they call for either a new waste waterpurification plant construction or at least considerable buildingrearrangements in the classical municipal waste water purificationplants. That's why an urgent need to create a solution enabling the useof the hitherto existing municipal waste water purification plants,which would at the same time fulfill the contemporary ecologicaldemands, has arisen.

The object of present invention is to eliminate as much of thedisadvantages of the known solutions as possible and to create a newmethod and apparatus realizing an essential intensification ofbiological activation waste water purification also with a possibilityto use already existing classical waste water purification plants.

SUMMARY OF THE INVENTION

The subject matter of the method according to the invention is that theactivation mixture is brought into circulation in a circulation circuit,at least a part of the circulation circuit intended for denitrificationand nitrification having a plug flow character and being formed bysequentionally ordered longitudinal flow channels provided by pneumaticaeration by means of aeration elements, at the end of the part havingthe plug flow character the purified water is taken away by a fluidizedbed filtration and sludge separated by the fluidized bed filtrationmixed with the activation mixture in form of a concentrated activationmixture is taken by forced flow means into the beginning of the firstflow channel, into the same place at the beginning of the first flowchannel raw waste water being brought.

Considering the effectiveness of the waste water purification it is acontribution that in the same time period the quantity of the purifiedwater which is being taken away from circulation circuit through thefluidized bed filtration is smaller than the quantity of the activationmixture circulating in the circulation circuit.

It is advantageous that the activation mixture mixed with the raw wastewater is oxidized gradually through the aeration with a simultaneoussuspendation of the activated sludge until the concentration of thedissolved oxygen in the activation mixture is at least two milligrams ofoxygen per one liter of the activated mixture.

Considering the control over the waste water purification process it isessential that the aeration is executed by a pneumatic aeration with avarying intensity as a function of the time and/or place in thecirculation circuit.

To reach a needed effect of the activation it is essential that thecirculation intensity of the activation mixture is at least the doubleof the purified water throughput.

Considering the bringing of the activation mixture in the plug flow itis a contribution that the activation mixture is brought into thecirculation circuit by the raw waste water admission, by draining offthe purified water and by forced admission of the activation mixturethickened by the separation into the circulation circuit behind theseparation process.

To increase the effectiveness of the denitrification it is significantthat the purified water is taken away during each circulation byfluidized bed filtration from oxid part of the circulating activationmixture.

The subject-matter of the apparatus according to the invention is thatalways two separation spaces are arranged adjacent to each other bytheir longitudinal sides, in which communicative connections with theactivation space are formed and the longitudinal distribution channel 5,formed between the said longitudinal walls is completely closed by anend wall at one side, while at the opposite side a passage is arranged,by means of which it is connected with the flow channels system, thechannels being laterally parted from the separation space, and the flowchannel system and at least one distribution channel 5 form a part ofthe circulation circuit, another part of the circulation circuit beingformed by a collecting equipment connected to the outlet for theactivation mixture from the separation space, said collecting equipmentbeing connected to at least one pumping set, the mouth of which formsthe beginning of the circulation circuit, while the raw water admissionmouths either into the admission area of the pumping set or into itsmouth area, and the circulation circuit is provided with at least onebaffle plate.

To keep the sludge at a sufficient age and the circulation intensity inthe circulation circuit it is advantageous that the collecting equipmentis arranged near to the bottom of the separation space for fluidized bedfiltration, the communicative connection with the activation space beingformed by the upper opening and the lower opening, both of which arelocated at the same side of the separation space, the upper opening isconnected with the extension of the separation space and the loweropening is near to its bottom, while the upper opening is smaller thanthe lower opening, so that it forms a resistance against the streamingof the activation mixture.

Considering the hydraulic relations in the reactor and the simplicity ofthe construction of the separation space it is substantial that theseparation space is connected with the activation space through apassage formed by a break in the partition of the separation space atthe tank bottom, while a collecting main with inlets for thickenedactivation mixture is arranged in the separation space near to the tankbottom, the collecting main being connected with a pump, the outlet ofwhich mouths in the activation space.

Considering the construction and reconstruction of waste waterpurification plants it is essential the circulation circuit is formed byat least one basic module, in which the distribution channel 5 is formedby two inner partitions and the outer partitions form always togetherwith the inner partition a separation space and together with thecircumferential wall of the tank or with the outer wall of the nextmodule a circumferential flow channel, while the distribution channel 5is at its front connected with the circumferential flow channel and atits side with the separation space.

Considering the effectiveness of the biological purification it isessential that the collecting sump, provided with a pump, is arranged inthe circulation circuit, while outputs of the collecting equipment,bringing the activation mixture, mouth in said sump, and the outlet fromthe pump mouths behind the baffle plate at the beginning of the flowchannel, the raw water admission mouthing in the collecting sump.

To provide a unified system for inner structure of reactors it isadvantageous that additive modules of an identical embodiment areadjoined in the perpendicular direction to the basic module, eventuallythe basic module is arranged with its axis going through the center ofthe tank and the additive modules are arranged symmetrically andperpendicularly to the basic module. It is also an advantageousembodiment wherein at least one additive module is parallel adjoined tothe basic module, the system of parallel modules formed in this waybeing symmetrical to the axis going through the center of the tank.

To maintain a link-up of the separate processes of the waste waterpurification it is essential that the aeration elements are in theadmission area for the raw waste water arranged with farther spacingthan in the next parts of the circulation circuit, the cross sectionalarea of flow of the inlet opening into the fluidized bed filter beinglarger than 10% of the surface area in the separation space.

An improvement of the denitrification course is reached by providing thecollecting equipment with at least one pump, preferably centrifugalpump, which is arranged in the collecting sump.

Considering the construction of big municipal waste water purificationplants it is a contribution that the separation space for fluidized bedfiltration is arranged through the whole length of the distributionchannels of the circulation circuit, while the inlet of activationmixture into the separation space for fluidized bed filtration and thecollecting equipment for carrying the thickened activation mixture outfrom the separation space are formed through its whole length.

For the effective removal of floated sludge is good that a trap forflotated sludge is arranged in the upper part of the separation space,said trap being formed by a sloping roof, to the lower side of which apressure air supply is adjoined, the upper part being provided with aflotated sludge outlet in the form of an air-lift pump mouthing in theactivation space, while the whole roof is under the tank surface area.

For preventing the influence of the flow in the distribution channel 5onto the flow pattern in the separation space it is important that atleast one flow deflector is arranged in the area of the passage to thepartition from the side of the activation space.

Considering the intensity of the nitrification it is advantageous that amixer is arranged at the beginning of the activation space and theoutlet from the pump mouths in the mixer, in which admission for rawwaste water mouths and the outlet from the mixer mouths in the followingpart of the activation space.

Due to the possibility of cleaning the collecting pipes it is importantthat the pump aggregate is a pump provided with a submersible reversibleelectric motor.

For the possibility of taking off the electric motor and the runner ofthe pump aggregate it is advantageous that the reversible electric motorand the runner of the pump are arranged slidingly on guiding bars,located vertically to the tank bottom.

Considering the keeping an optimal length of the collecting pipes it isimportant that the pump is connected with at least two branches of thecollecting main.

To enable an interrupted or controlled supply of the air it is importantthat the aeration hoses are located in the activation space and areconnected with the pressure air supply through a closing or through aregulator.

For better use of the air oxygen it is important that the aeration hosesare arranged in two branches which are located mutually at the oppositesides of the cross-section of the circumferential channel.

The method and apparatus according to the invention represent a veryeffective means for prevention the eutrophication in the water suppliesin the nature. The main advantage is a high effectiveness of thepurification for both removal of the the organic substances from thewaste water and reducing the content of the eutrophication elements,i.e. nitrogen and phosphorus. A complex waste water purification,especially municipal waste water purification is hereby provided by asimple method for activation purification without the necessity to addadditional procedures for denitrification and dephosphatisation. Thissignificantly simplifies the technical solution of the reactors for acomplex biological waste water purification.

The module system of the reactor according to the invention allows amodular construction of the reactors in a wide range of capacity, up tothe biggest reactors suitable for conurbations with millions ofinhabitants. With channels formed by insertion the separation spaces forfluidized bed filtration into the activation space, the system ofchannels conection into a uniform circulation circuit allows a maximumsimplifying and at the same time a shortening of the connecting waysbetween the linking up processes of the activation purification,including separation of the activated sludge with a minimum hydraulicresistance in the system. The system of activation mixture circulationallows also a spot inlet for raw water into the reactor, which lowersthe cost of the raw waste water distribution in the waste waterpurification plant.

Another advantage of the method and apparatus according to the inventionis a high capacity resulting from a maximum use of the surface area ofreactor for separation, allowing the reactor working with a highactivated sludge concentration, which causes an increased qualitativeand quantitative parameters of the apparatus.

The method and apparatus according to the invention allow also areconstruction of the hitherto existing classical waste waterpurification plants, which means an essential cost reduction comparedwith a construction of new waste water purification plants or anextension of old waste water purification plants.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference toexemplifying embodiments thereof, illustrated in the accompanyingdrawings, in which

FIG. 1 is a ground view at the basic module of the circulation circuitof the activation mixture;

FIG. 2 is a vertical section through the module along the line A--A inFIG. 1;

FIG. 3 is a vertical section along the line B--B in FIG. 1;

FIG. 4 a vertical section along the line C--C in FIG. 1;

FIG. 5 is a axonometric view at the basic module of the circulationcircuit according to FIG. 1 to 4;

FIG. 6 is a front view at the flotated sludge trap;

FIG. 7 is a sectional view along the line D--D in FIG. 6;

FIG. 8 is a top view at the reactor with a rectangular ground planresulting from adjoining other modules of the circulation circuit to thebasic module of the circulation circuit;

FIG. 9 is a vertical section through the reactor along the line A--A inFIG. 8;

FIG. 10 is a vertical section along the line B--B in FIG. 8;

FIG. 11 is a vertical section along the line C--C in FIG. 8;

FIG. 12 is an oblique view at another embodiment of the reactor withpartial cuts; and

FIG. 13 is a schematical transversal crossection through the embodimentshown in FIG. 9.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENT

The apparatus according to the present invention comprises at least onecirculation circuit. Each circulation circuit includes at least onebasic module. In case the apparatus includes more modules or eventuallyone basic module and other additional modules, the embodiments of thebasic module and the additional modules are preferably identical.

In the embodiment of the basic module of the circulation circuitaccording to FIGS. 1 to 4 is the volume of a rectangular tank with thecircumferential walls 1, e.g. concrete walls, and with the bottom 8divided by a system of inserted partitions 2 into functional spaces,i.e. spaces for both biological activation waste water purificationprocesses and for flocculent suspension separation by a fluidized bedfilter.

In a preferred embodiment of the basic module, the adjacent innerpartitions 2 delimitate the separation spaces 4, which create thefluidized bed filter, each of them having a circumferential flow channel7 passing along one of its sides and a distribution channel 5 along theother side, which ends up in the face 6, which completely closes theseparation space 4 for fluidized bed filtration and the distributionchannel 5. There are two separation spaces 4 abutting on each other bytheir longitudinal sides in the basic module, wherein the distributionchannel 5 is formed between them. Separation spaces 4 spread essentiallythrough the whole length of the basic module and communicate essentiallythrough the whole length with the distribution channel 5. Thecircumferential flow channels 7 are located between the outer partitions2 and the circumferential walls 1 of the tank and they are separatedfrom the separation spaces 4 along their sides. The trap 29 for flotatedsludge and the collecting flumes 15 for collecting the purified waterare located in the upper part of the separation spaces 4 for fluidizedbed filtration.

The separation space 4 for fluidized bed filtration is completely closedby the face wall 6' at the opposite end, while the distribution channel5 communicates with the circumferential flow channel 7 through thepassage 26. The passage 26 has a rectangular shape, the longer sidethereof being vertical (FIG. 3). This embodiment is easy to produce andis functionally satisfying. But the passage 26 may also have a differentshape, e.g. the shape referring to the cross section of the distributionchannel 5 in order to achieve a minimum hydraulic resistance.

There may be also formed a not shown module comprising only oneseparation space 4. In that case the circumferential flow channel 7 isformed along a longer side and a shorter side of the separation space 4while the distribution channel 5 is formed along the other longer side.By arranging two of these not shown modules side by side the abovementioned basic module with two separation spaces 4 results.

The flotated sludge trap 29 (FIG. 6,7) is immersed under the surface. Itcomprises a sloping roof with the head 40 (FIG. 7). The essential partof the roof is horizontal, while the head 40 connected with theessential part or forming a single unit with it is inclined, its crosssection thus gradually altering. The head 40 is at a relatively smallangle with the horizontal plane. The lower ending of the trap 29 isconnected through the admission 38 with a not shown separate pressureair supply with an overpressure corresponding to a comparatively smallimmersion depth, that means that the trap 29 is aerated. At theopposite--higher ending of the trap 29 an outlet for flotated sludge islocated, the main part of which is the air-lift pump 39, preferablyconnected with the same pressure air supply as the admission 38. Theair-lift pump 39 may also be connected with another separate pressureair supply (not shown). The terminal of the air-lift pump 39 is led outat optional place at the flow channels 7,9. Sludge withdrawal may becontinuous or intermittent, i.e. the pressure air supply, eventuallypressure air supplies may be active permanently or intermittentlyessentially in dependence on the flotation rate. The present inventionmay be used also without the trap 29, e.g. in a case where no increasedsludge flotation in the separation occurs.

The partitions 2 are angular in the upper part of the separation space 4(FIG. 2,3,9,10). The lower part 12 of the separation space 4 is linkedto the upper part, the partitions 2 in the lower part 12 beingpreferably straight and parallel to each other. There is the upperopening 10 formed in the upper part of each separation space 4 and thelower opening 11 in the lower part 12. Both openings 10, 11 form acommunication connection from the distribution channel 5 to theseparation space 4 and they are both at the same side of the separationspace 4. The upper opening 10 is linked to the extension of theseparation space 4 and forms thus at the same time the inlet foractivation mixture into the separation space 4. Said upper opening 10 isas a rule provided by a smaller inlet cross section than the loweropening 11, the upper opening 10 causing an additional resistance forthe activation mixture streaming from the distribution channel 5 intothe separation space 4 (FIG. 2,3). The upper opening 10 forms preferablya slot spreading through the whole length of the separation space 4,eventually an intermittent slot or separate, uniformly located slotopenings. The axis of the lower parts 12 of the separation spaces 4 ispreferably vertical, but it may be also oblique, so that the lower part12 of the separation space 4 is deviated from the distribution channel5. The lower opening 11 is arranged near to the bottom of the separationspace 4, it is realized as openings in the wall of the lower part 12 ofthe separation space 4 and its total cross-section is larger than totalcross-section of the upper opening 10 up to its multiple. The loweropening 11 is intended particularly for drawing the activation mixtureinto the lower part 12 of the separation space 4, for equalizing thelevels in the separation space 4 and in the activation space and alsofor sludge removal when the operation is interrupted.

The size of the inlet opening 14 into the fluidized bed filter is in thebig municipal waste water purification plants--with a low hydraulicunevenness factor up to 1.5--at least 10% of the separation surface.

The outlet for the thickened activation mixture from the separation isconnected to at least one collecting equipment with at least one pumpingset. According to a preferred embodiment the collecting mains 13 of thecollecting equipment are located near to the bottom of the lower parts12, the collecting mains being connected with collecting sump 35,wherein at least one pump, preferably a centrifugal pump 36, is located,and this pump is also a source of local turbulence. Outlet 27 of thepump 36 is directed to the circumferential flow channel 7 behind thebaffle plate 28 as viewed in the direction of the activation mixtureflow (FIG. 1). Baffle plate 28 closes the head of the circumferentialflow channel 7, either completely, which is a preferred embodiment, orat least partly. It is essential that the outlet 27 together with theadmission 22 for the raw sludge mouths in the circulation circuit in theflow direction behind the separation spaces 4. So the raw wateradmission 22 may mouth either in the inflow area of the pumping set orin the outlet area of the pumping set behind the baffle plate 28. Theraw water admission 22 is preferably directed in the collecting sump 35(not shown in FIG. 1).

The distribution channel 5 communicates through the upper opening 10with the separation spaces 4 and through the lower opening 11 with thecollecting main 13 (FIG. 1,8), wherein at least one pump is included asa pumping set, e.g. an air-lift pump (not shown) or more air-lift pumps(not shown), eventually the said centrifugal pump 36 located in thecollecting sump 35 (FIG. 1,8,11), as mentioned above. If the centrifugalpump 36 located in the collecting sump 35 is put into practice, noair-lift pump is used, eventually the air-lift pump is included in someof the branches of the collecting main 13 only in order to increase themixing effect in the thickened activation mixture leaving the outlet 27and falling in the activation mixture in the tank, eventually into thecollecting sump 35. The air-lift pump--or the centrifugal pump 36, ifthe collecting sump 35 is included--mouths with its outlet 27 into thecircumferential flow channel 7 behind the baffle plate 28 (FIG. 1). Thecentrifugal pump 36 may also be replaced by the air-lift pump. Bothkinds of pumps may be located either in the collecting sump 35 oroutside the collecting sump 35, in every case the pump is a part of theoutlet from the collecting sump 35, adjoining thus the collecting sump35.

Through this mutual connection between the circumferential flow channel7, distribution channel 5, separation spaces 4 and by means of thecollecting main 13 of the collecting equipment and the collecting sump35 through back connection through outlet 27 with the circumferentialflow channel 7, a circulation circuit for the activation mixture isformed, wherein the activation mixture flows in a plug flow. Thecircumferential flow channel 7 is over the whole length completelyseparated from the separation spaces 4 by the partition 2.

The aeration elements 3 are placed near to the bottom in thecircumferential flow channel 7 and in the distribution channel 5,preferably with various spacings so that different sections of thecirculation circuit have different aeration intensity. According to thepreferred embodiment the aeration elements 3 are in the raw sludgeadmission area located so that they are spaced farther from each otherthan in the next parts of the circulation circuit.

It is also possible to locate the aeration elements 3 with equalspacings but with different aeration intensity at different places ofthe circulation circuit, the inventive apparatus may be thus adapted todifferent conditions. It is also possible to use aeration elements witha time variable aeration intensity.

The above mentioned baffle plate 28 is located in the circumferentialflow channel 7 at the face wall 6' side with the passage 26 into thedistribution channel 5. There is a raw water admission 22 leading behindthe said plate 28 together with the outlet 27 of the air-lift pump orair-lift pumps (not shown), eventually the centrifugal pump 36. Thecircumferential flow channel 7 has got in its longitudinal parts alongthe separation spaces 4 a form of a narrow corridor, its cross sectionbeing formed by the shape of the separation space 4. As a rule thecircumferential flow channel 7 extends downwards first (FIG. 2) and inthe lower part its walls are vertical and parallel. If using a differentform of the separation space 4, the walls of the circumferential flowchannel 7 may be e.g. angular and parallel, eventually angular anddivergent.

The operation of the described basic module of the circulation circuitand the method for biological activation waste water purification with adynamic nitrification and denitrification is as follows:

The activation mixture circulates in the circulation circuit by a plugflow and it is continuously oxidized by a pneumatic aeration, which atthe same time secures a suspendation of the activated sludge. So allindividual particles of the activation mixture advance in thecirculation circuit with at least one vector component of its speed inthe direction of the activation mixture flow as a whole in thecirculation circuit. It is thus advantageous that through the operationof the aeration elements 3 the individual particles move also in thelevel perpendicular to the advance in the circulation circuit andperform e.g. a helicoid movement. To reach a high activated sludgeconcentration in the circulation circuit, the activation mixture isobject of fluidized bed filtration in course of every circulation,during which the purified water is separated from the mixture, while theseparation is performed in the separation spaces 4, which coverpractically the whole surface of the tank with the circumferentialwalls 1. Purified water separated through fluidized bed filtration istaken away by collecting flumes 15 and its quantity is always lesserthan quantity of the activation mixture circulating in the circulationcircuit during the same time period. It is advantageous that thepurified water is taken away by the fluidized bed filtration from a partof the circulating activation mixture only, what enables to reach a highcirculation intensity and herewith high denitrification degree ispossible. This is achieved according to the exemplifying embodiment bydrawing the activation mixture from the distribution channel 5 throughthe lower opening 11 in the collecting equipment area near to the bottomof the separation space 4.

The circulation is performed by raw waste water admission, by pumpingthe thickened activation mixture from the fluidized bed filter back intothe circulation circuit behind the baffle plate 28 and by purified wateroutlet through the collecting flumes 15. The activation mixture isherewith brought in the circulation circuit with a plug flow character.Raw waste water is admixed into the circulation circuit, preferablybehind the baffle plate 28 or in the collecting sump 35. That causes anoxygen lack at the surface of the particles of the activated sludge, andit starts denitrification processes. The activation mixture is then byeffects of the aeration elements 3 gradually oxidized by aeration withsimultaneous suspendation of the activated sludge during the circulationin the flow channels 7 till the conditions necessary for nitrificationprocesses are reached, and then the activation mixture is subjected to afluidized bed filtration in the separation spaces 4. Raw waste water isadmixed into the thickened activation mixture with nitrate originatedthrough the oxidation of the nitrogen pollution, e.g. in the collectingsump 35, and herewith all processes of the complex waste waterpurification with organic and nitrogen substances removal are realizedduring one circulation. As a rule the activation mixture is graduallyoxidized through the aeration until the concentration of the oxygendissolved in the activation mixture reaches or exceeds at least twomilligrams of oxygen per one liter of the activation mixture. Herewithan optimum process of biological waste water purification is realized,as it will now be below described in more detail.

The activation mixture enters the separation spaces 4 for fluidized bedfiltration through the upper opening 10 and the extending space of theseparation space 4, and it is brought through the inlet opening 14 fromthe lower part 12 into the extending part of the separation space 4,wherein the fluidized bed filtration is realized. The effectiveness ofthe separation through the fluidized bed filtration depends among otherson the size of the inlet opening 14. The optimum size of the inletopening 14 is at least 10% of the separation surface in big municipalwaste water purification plants with a low hydraulic unevennesscoefficient up to 1.5. The separation of purified water from theactivated sludge is performed in the fluidized bed filter in theseparation space 4 by fluidized bed filtration, wherein the waterdeprived of the activated sludge suspension is led away throughcollecting flumes 15 from the purification system. The flotated sludgeintercepted on the trap 29 is brought into the activation space, as arule at an arbitrary place in one of the flow channels 7,9. Throughfiltration thickened activated sludge sinks countercurrent-wise throughthe inlet opening 14 into the lower part 12 to the collecting main 13arranged near to the bottom of the lower part 12. The outlet 27 of thecollecting equipment, eventually in absence of a pump, the collectingmain(s) 13 itself mouths in the collecting sump 35, wherefrom theactivation mixture is pumped off by a centrifugal pump 36, this pumpcausing a strong local turbulence.

The local turbulence excited by the centrifugal pump 36 is necessary torelease gaseous nitrogen bubbles which stuck at the particles of theactivated sludge during the denitrification process. The flowing of theactivation mixture in the collecting sump 35 is of a gravitational typeowing to a difference between the level in the tank and in thecollecting sump 35. If the local conditions call for it, it is alsopossible to place a pump in the collecting equipment, e.g. an air-liftpump.

The lower opening 11 allows also in case of an interruption in thereactor aeration a passage of the activated sludge from the separationspace 4 into the distribution channel 5, and herewith an undesirablesilting with sludge in the lower part 12 is prevented. The lower opening11 secures at the same time a level equalizing in separation andactivation during the filling of the reactor or during the sludgeblow-off, and this allows a pressureless solution of inner structure ofreactor.

Raw waste water is admixed in the circulation circuit in thecircumferential flow channel 7 into the activation mixture thickenedafter the fluidized bed filtration, said waste water causing a shockdrop of the dissolved oxygen concentration in the activation mixtureespecially at the surface of the particles of the activated sludge, andherewith it provides good conditions for dynamic denitrification. Thedenitrification processes nevertheless don't require anoxid conditionsin the whole volume of the activation mixture, formation of local anoxidconditions at the surface, eventually at the surface of the activatedsludge particles is entirely sufficient. The shape of thecircumferential flow channel in the form of a narrow corridor makes itpossible that also a little aeration intensity is sufficient for asuspendation of the activated sludge during a considerable flowing speedof the activation mixture. The denitrification regime needing a lowoxygen content in the activation mixture is not impaired by that.

At the running aeration during the plug flow it comes to abiodegradation of the polluting substances in the activation mixturethrough oxidation and a gradual saturation of the activation mixturewith oxygen up to the reaching of conditions for nitrogen substancesnitrification, what is usually achieved through a value over 2 mg O₂ /l.An increased content of the dissolved oxygen is favorably shown also inthe effectiveness of the following activated sludge separation throughthe fluidized bed filtration, because a higher oxygen content in theactivation mixture prevents denitrification processes during thefluidized bed filtration. It prevents the flotation of the activatedsludge in the separation space 4 and also the releasing of thephosphorus into the purified water.

The circulating activation mixture brings nitrates, originated in thenitrification zone with sufficient oxygen content, into the circulationcircuit zone with a lowered dissolved oxygen content. Then the nitratesare reduced to a gaseous nitrogen in said zone with a lowered oxygencontent, and so the denitrification is performed. Bubbles of the gaseousnitrogen which stick at the activated sludge particles during thedenitrification are removed with the circulation of the activationmixture in the circulation circuit by a movement supply with a highlocal turbulence intensity, e.g. by a centrifugal pump 36. The streamingpower for calling intensive local turbulences may be advantageously usedfor admixing the circulating activation mixture with the purified wastewater, wherein the raw waste water admixed into the circulatingactivation mixture causes besides a lowering the content of dissolvedoxygen, also carbon supply necessary for denitrification processes.

The effectiveness of the described dynamic waste water denitrificationin the circulation cycle of the activation mixture with periodicalalternation of the nitrification and denitrification process depends onthe circulation intensity of the activation mixture according to theexpression ##EQU1## wherein τ is the effectiveness of thedenitrification given in percents

n is the proportion of the water quantity running through one crosssection in the circulation circuit in a time unit to the raw waterquantity being brought in the same time unit.

This proportion represents a circulation intensity in the circulationcircuit. E.g. to reach a 75% effectiveness of the nitrates reductionaccording to the above mentioned expression a triple circulationintensity compared with the purified raw water quantity is necessary.Described process of biological waste water purification is usuallyeffective with an intensity of the activation mixture circulation beingwithin the range of double up to sextuple of the purified waterquantity. The circulation intensity may be also much higher for veryconcentrated waste water and therefore the quantity of the water runningthrough the circulation circuit may be a multiple of the raw waste waterbeing brought. Then it is also necessary that the sucking of theactivation mixture through lower opening to the collecting equipmentinlet is higher. That is given by the dropping resistance value, i.e. bythe size of the upper opening 10.

The total intensity of the biological purification processes depends onthe concentration of the activated sludge in the purification system,which is directly dependent on the separation intensity. The circulationof the activation mixture in the circulation circuit necessary to reachthe required denitrification intensity increases the claims forseparation capacity.

An integral insertion of the fluidized bed filtration in the circulationcircuit of the activation mixture, with a full use of the wholeactivation surface for separation, secures a high concentration of theactivated sludge, which secures then a low sludge loading necessary forthe nitrification as the main objective for nitrogen pollution removalfrom waste water. An important quality of the described method ofdynamic nitrification and denitrification is also its high effectivenessof phosphates removal from waste water, that with a total reduction ofphosphorus up to 80%.

According to the described method all processes of complex biologicalpurification with a removal of organic and nitrogen substances and alsowith a high effectiveness of phosphates removal from waste water areaccomplished in one circulation in the circulation circuit.

Example of the Method No. 1

The described method according to the invention performed in a communalwaste water purification plant of a mountains recreation center, andbefore all documentation of results of this method is in question. Forthe waste water purification plant a seasonal load is characteristicwith maximum values in winter and summer. The top hydraulic load is 200m³ in an hour and in a period out of season it is 100 m³. Such a planthas also remarkable deviations of the substance load with maximum valuesin summer and winter. The average concentration of the pollution inseason or out of season shows the following table I.

                  TABLE I                                                         ______________________________________                                                season      out of season                                             sort of   inlet   outlet     inlet outlet                                     pollution mg/l    mg/l       mg/l  mg/l                                       ______________________________________                                        BOD.sub.5 488,0   6,3        116,0 2,6                                        COD       951,0   28,0       269,0 15,8                                       SS        606,0   17,0       165,0 9,0                                        P tot      7,0    0,53        2,6   0,35                                      N--NH.sub.4.sup.+                                                                        36,0   3,90        8,9   0,48                                      N--NO.sub.3                                                                               0,17  9,50        0,3  7,0                                        N--NO.sub.2                                                                               0,01  0,05         0,03                                                                               0,03                                      N org      22,0   2,0         8,0  1,8                                        N tot      57,0   15,5        17,2 9,3                                        ______________________________________                                    

where

BOD₅ is biological oxygen demand in five days per one kilogramme ofvolatile suspended solids of the activated sludge

COD is chemical oxygen demand

SS suspended solids

P tot total amount of phosphorus in the waste water

N org amount of the organic bound nitrogen

N tot total amount of nitrogen

Example of the Method No. 2

The described method of the biological purification used for pig manurepurification is in question. The pig sewage presents an example ofextraordinarily polluted waste water having a concentration of organicsubstances, nitrogen and phosphorus, which exceeds the concentration ofthe communal waste waters in the order. Again the documentation of theresults of the method according to the invention is in order.

The input values of the pig manure after a mechanical separation of therough components show the table II.

                  TABLE II                                                        ______________________________________                                                   amount in mg/l                                                     ______________________________________                                        COD          24170                                                            BOD.sub.5    7500                                                             SS           9390                                                             N--NH.sub.4.sup.+                                                                          1060                                                             N tot        1640                                                             P tot        1970                                                             ______________________________________                                    

A controlled system of aeration was used, namely gradually differentintensity of the aeration in the circulation circle with the controlledtime course of the aeration according to the invention. At the outletfollowing parameters of water mentioned in table III were achieved.

                  TABLE III                                                       ______________________________________                                                   amount in mg/l                                                     ______________________________________                                        COD          160                                                              BOD.sub.5    20                                                               SS           5                                                                N--NH.sub.4.sup.+                                                                          20                                                               N tot        30                                                               P tot        3                                                                ______________________________________                                    

The embodiment according to FIG. 8 to 11 is a modular one, based on thebasic module of the circulation circuit. An increase of the reactorcapacity is obtained by adding other modules of the circulation circuitto the basic module.

The number of adjoint modules may vary and so it is possible to form areactor in a modular way with a capacity responding to a need. Apreferred solution is formed by a multi-unit arrangement of severaladjoint modules without another partition between them, as shown incross section in FIGS. 9,10.

In that exemplifying embodiment right-angled tank having circumferentialwalls 1 is divided by a system of inserted partitions 2 into functionalspaces for activation biological processes of waste water purificationand for separation of flocculent suspension by a fluidized bed filter inthe same way as in the basic module in the circulation circuit. What isdifferent is that the separation spaces 4 divide the activation space indistribution channels 5 and new inlet flow channels 9, wherein thedistribution channels 5 are the same as in the single basic module,while the inlet flow channel 9 is not present in the single basic moduleand it is formed essentially by two opposing circumferential flowchannels 7 of the basic module. The distribution channels 5 and theinlet flow channels 9 are closed at one end by faces 6, which entirelyclose the separation spaces 4 and the distribution channels 5.Nevertheless, the faces 6 are interrupted at the end of the inlet flowchannels 9, forming passages 25, by means of which the inlet flowchannels 9 are connected with the circumferential flow channel 7 (FIG.8). The passages 25 have got the same form as the passages of the basicmodule. The flow channels, e.g. the circumferential flow channel 7 andthe inlet flow channel 9, are in all embodiments at their longitudinalsides entirely separated from the adjoining spaces, especially from theseparation spaces 4.

The flow channels are designated as inlet flow channel 9 andcircumferential flow channel 7 just to make the arrangement clear,because the circumferential channel 7 is arranged along thecircumferential wall 1 of the tank and the activation mixture enters theinlet channel 9 before it enters the distribution channel 5. But thedesignation "flow" is more essential for both of said channels becauseboth are intended for plug flow of the activation mixture, withoutpermission the activation mixture to get away from these flow channels7,9 and also without changing the flow volume in these seriallyconnected channels.

The separation spaces 4 and the inlet flow channels 9 are at the otherend quite closed by the face walls 6'. These face walls 6' are alsointerrupted and thus at the places of the interruption form the passages26 in a similar way as in the above mentioned basic module, wherein thedistribution channels 5 communicates through the passages 26 with thecircumferential flow channel 7. The separation spaces 4 for fluidizedbed filtration are connected with the distribution channels 5 in thesame way as in the basic module. There are no circumferential wallsbetween the adjoint modules of the circulation circuit--in theexemplifying embodiment of the reactor there are three modules--so thatby adding two modules to each other the flow channel 9 arises, asmentioned above.

The module in the embodiment according to FIGS. 8 to 11 perpendicular tothe adjoint modules is modified. Unlike the individual basic moduleaccording to FIGS. 1 to 5 this modified basic module has no passage 26formed in the face wall 6', so that the distribution channels 5 areclosed at both sides. So the distribution channel 5 of this modifiedbasic module (FIG. 8) does not communicate with the circumferential flowchannel 7 of the modified basic module. In addition the separationspaces 4 are divided into two parts, a collecting sump 35 being arrangedbetween them. There are two baffle plates 28 used therefor (FIG. 8).

The modified basic module is separated from the adjoint modules systemby a partition wall 34, wherein passages 41 indicated by arrows in FIG.8 are formed. The passage 41 connects always the circumferential channel7 of the modified basic module with the beginnings of the inlet flowchannels 9 of the adjoint modules. The circumferential flow channel 7 ofthe adjoint modules is connected through the interconnection 30, forexample through pipes, with the distribution channels 5 of the modifiedbasic module (FIG. 8). The outlets 27 of the collecting mains 13 mouthin the collecting sump 35. It is also within the scope of presentinvention to form another modification of connections between theadjoint modules and perpendicular modified basic module.

The function of the reactor according to FIG. 8 to 11 is essentiallyidentical with the function of the basic module in the circulationcircuit described above. Raw waste water is brought into the collectingsump 35, wherefrom the waste water, mixed with thickened activationmixture, is discharged into the area between collecting sump 35 and thepartition wall 34. It flows further towards the circumferential flowchannel 7 of the modified basic module--in FIG. 8 below. It flows thenin both sides through the circumferential flow channel 7 as far as tothe partition wall 34 and through the passages 41 in said partition wallinto the inlet flow channels 9 of the adjoint modules (FIG. 8),wherefrom it comes into the circumferential flow channel 7--as shown inFIG. 8 above. The activation mixture flows out of it further through thecircumferential flow channels 7 along both sides of the tank. Itadvances further through the circumferential flow channel 7 along themodified basic module and enters the distribution channels 5 of theadjoint modules through the passages 26 and also the distributionchannels 5 of the basic module through the interconnection 30--formedfor example by pipes. The activation mixture comes from the distributionchannels 5 into the separation spaces 4, as mentioned above. Thethickened activation mixture from the separation spaces 4 is brought bythe collecting equipment, especially by the collecting main 13 andoutlets 27, into the collecting sump 35.

Another alternative of the apparatus according to the present invention(not shown) has a circular tank, wherein the flow channels 9,7, thedistribution channels 5 and the separation spaces 4 are arranged similarto the embodiment shown in FIG. 8 with the difference that the length ofthe separation spaces 4 and the shape of the circumferential flowchannels 7 are adapted to the tank shape. Said embodiment is suitablemostly for reconstructions of circular sedimentation basins common e.g.in already existing and used municipal waste water purification plantsof the classical type, to increase their quality and quantityparameters. Through reconstruction of the circular sedimentation basinsin the hitherto existing municipal waste water purification plants it ispossible to keep the original raking bridge (not shown) and to use it toaccess the individual places of the reactor tank doing the operationalcontrol.

The function of the reactor is at the same time essentially identicalwith the function of the preceding exemplifying reactors describedabove, especially with that of the reactor according to FIG. 8 to 11.

Another variant of the apparatus according to the invention is shown inFIG. 12 and 13.

In the rectangular tank with the circumferential wall 1 are throughinserted partitions 2 and face walls 6 and 6' created two longitudinalseparation spaces 4, spreading out in the upwards direction. Thepartitions 2 are advantageously in their lower parts connected to thebottom of the tank and with their upper parts to a not shown carrierconstruction. Separation spaces 4 create in the tank between thepartitions 2 and face walls 6,6' the distributing channel 5, which is apart of the activation space. The face wall 6 of the separation space 4reaches up to the circumferential wall 1 and creates thus the partitionwall 28, which similarly to the previous alternative separates thecircumferential flow channel 7. The other face wall 6' closes not onlyseparation spaces 4, but it separates also the distribution channel 5from the circumferential flow channel 7. The circumferential flowchannel 7' is a through flow channel, it does not communicate with anyother space except of distributing channel 5, which is linked to it.

In the opposite face wall 6 an inlet 24 to the distribution channel 5 iscreated. The separation space 4 is along to its complete lengthconnected with the distribution channel 5 and due to it also with theactivation space through the only one passage 19, which is arranged inat least one breaking of the partition 2 at the bottom of the tank (FIG.13). The passage 19 can be either along its length without break or itcan be made as a set of orifices in the partition 2 of the separationspace 4.

Partitions 2 have in the cross section advantageously an arc form (FIG.12). The partitions 2 expand from each other in the upwards directionand they thus create the prismatic separation space 4 for the fluidizedbed filter. The partitions 2 are at the same time at the bottomseparated from each other and between them is at the bottom arranged theperforated collecting piping 13, which is mouthed to the pumpingaggregate 25. The partition 2 can be made from a smooth material or froma profiled material. It is advantageous to make the profilation in thedirection from above to bottom, what ensues in forming of low ribs onthe surface of the partitions 2.

In the area of the passage 19 at least one flow rectifier 20 is added tothe partitions 2 from the side of activation space, i.e. from the sideof distribution channel 5. It is determined for the separation of theflow of activation mixture in the distribution channel 5 from the flowin separation space 4. The flow rectifier 20 is advantageously attachedto the partition 2 and it is orientated vertically and it is extendingsubstantially along the full length of partition 2. It is possible toarrange along the length of partition 2 a number of flow rectifiers 20linking to each other. The flow rectifier 20 is arranged at the lowerpart of the partition 2, its lower edge being situated over the loweredge of partition 2, but it reaches at most to the level of edge of thepartition 2. It is nevertheless also possible to leave this flowrectifier 20 out. When the flow rectifier 20 is applied, it restrictsthe transfer of turbulence from the activation space to the separationspace. Its efficiency can be higher at the profiled partitions 2 or evenat smooth separation walls, where the profilation is made only in thearea of attachment of flow rectifier 20, where it is attached to theribs of profile of partition 2 and thus does not abut tightly to theseparation wall in the whole area of joint. In this way a small part ofactivation mixture between the flow rectifier 20 and partition 2 comesto the area of passage 19 and it supports the restriction of transfer ofturbulence from the distribution channel 5 of the activation space.

The pumping aggregate 41 consists of the pump body, in which thecollecting piping 13 is mouthed and which is attached to the bottom ofthe tank, and of a moving pump wheel which is connected through theshaft to an immersion electric motor, which is advantageously areversible one. Rotating parts of the pumping aggregate 41 are mountedwith the possibility of drawing them out above the level of the reactorduring its operation.

Into the pumping aggregate 41 the collecting piping from the otherseparation space 4 is mouthed, pumping aggregate 41 being thus common.In case of great length of the separation spaces 4 the pumping aggregatecan be advantageously placed in the middle of the length of thedistribution channel 5. In that case are to the pumping aggregate fromthe both neighored separation spaces 4 mouthed four collecting pipings13, always two and two from each side. At the great length of thereactor it is possible to arrange a number of pumping aggregates behindeach other in order to reduce the length of the collecting piping 13 to12 meters, what is the optimum length for the collecting system.

Power unit of the pumping aggregate 41 is the electric motor 42. On thenot shown carrier construction an elevating mechanism (not shown) isplaced. Reversible electric motor 42 and moving wheel of the pumpingaggregate 41 are mounted slidingly on the guide stabs, which arearranged perpendicularly to the bottom of the tank. Due to thiselevating mechanism it is possible to pull out the submerged reversibleelectric motor 42 and the moving wheel of the pumping aggregate 41 onthese (not shown) guide stabs even without the emptying of the tank.Pumping aggregate 41 and its power unit are modified for the reversiblemoving for the reverse flow of the activation mixture in the collectingpiping 13.

At the beginning of the distributing channel 5 and thus at the beginningof the activation space a mixer 46 for the mixing of activation mixturewith the raw waste water is arranged. The outlet 43 from the pumpingaggregate 41 is brought behind the partition wall 28 at the beginning ofthe circumferential channel 7 to the mixer 46, into which also the inlet22 of the raw waste water is mouthed.

Mutual interconnection among the circumferential channel 7, distributingchannel 5, separation space 4 and the collecting system, created by thecollecting piping 13 and pumping aggregate 41, forms an innercirculation circuit. From the above described results that thecollecting piping 13 could be specified also as a recirculation piping,because through it the activation mixture comes back to the circulationcircuit.

The circumferential channel 7 and the distributing channel 5 areequipped with an aeration system consisting of the row of perforatedelastic aeration hoses 47, connected to a common distribution system 44of the pressed air. The (not shown) orifices in the perforated elasticaeration hoses 47 are advantageously small for the creation of smoothbubbles by the aeration. Every aeration hose 47 is equipped with anindependent valve 45 or with a (not shown) regulator for the regulationof the aeration intensity. Through location of various numbers of theaeration hoses 47 in different places of the circumferential channel 7and the distributing channel 5, the aeration intensity according to theneeds of purification process can be influenced. Another regulation ofthe aeration intensity in dependence on the time can be achieved byinstallation of a (not shown) blower with a changeable speed of rotationor by installing of bigger number of blowers and by starting themaccording to the needs of aeration. At an advantageous arrangement ofthe aeration hoses 47 in the activation space the aeration hoses 47 arelocated in two branches, each of them can contain several aeration hoses47. These branches are arranges mutually at the opposite sides of thecross-section of the circumferential channel 7, regularly near at thebottom of the tank.

The upper part of the separation space 4 is equipped by the overflowchannels 15 for the removal of cleared water after fluidized bedfiltration.

The described alternative according to the FIGS. 12 and 13 worksanalogically with the previous alternatives.

The subject is an integrated reactor for biological waste waterpurification, wherein separation spaces 4 for the separation ofsuspension of the activated sludge by fluidized bed filtration arebuilt-in in the activation space. By building-in of separation spaces 4a system of channels is created, said channels being interconnectedserially behind each other by the above described manner.

The raw waste water is brought through the inlet piping to the mixer 46at the beginning of the circumferential channel 7 in the direction ofthe flow behind the partition wall 28, where the pumping aggregate 41also brings the recirculated activation mixture from the separationspaces 4 by. In the mixer 46 the raw waste water is perfectly mixed withthe recirculated activation mixture. The bringing-in of the organicsubstances present in the raw waste water to the activation mixtureinduces an intermittent decline of the content of the dissolved oxygen,whereby at the beginning of circumferential channel 7 anoxid conditionsfor the denitrification processes are created.

Suspendation of the activated sludge is in this anoxid part of theactivation kept by the aeration with a very low intensity, which issatisfactory for keeping suspension in suspendation, but anoxidconditions for a process of denitrification are not disturbed. Becauseof this the number aeration hoses 47 in this part of the circumferentialchannel 7 is reduced. For improving of the suspendation it is possibleto equip this part of the circumferential channel 7 by a not shownmechanical source of mixing, which eventually enables complete leavingout of aeration from this part of activation.

The course of the denitrification process is checked by measuring ofparameters of the activation mixture by using of probes (not shown),which bring the impulses to the power units of the blowers. In such away their speed of rotation and amount of supplied air is being changed.By the reduced intensity of aeration is the denitrification zone in thecircumferential channel 4 spread out, whereby the intensity ofdenitrification arises. This process can be fully automated.

During a plug flow of the activation mixture through the circumferentialchannel 7 the content of dissolved oxygen is gradually enhanced, thisprocess being a consequence of the enhanced intensity of aeration and ofthe decline of content of biodegradationable substances. In such a wayan oxide milieu for the aerobe activation processes of thebiodegradation of organic substances and for nitrification of ammoniacaland organic nitrogen is created. If the aeration hoses 47 are arrangedin two branches located at the opposite sides of the cross-section ofthe circumferential channel 7, it is possible by means of the valves 45or not shown regulators to bring the air alternatively into one branchand then into the other branch. During bringing the air for example intothe left branch a transverse circulating movement of the activationmixture originates. At interrupting the bringing of the air into theleft branch and bringing the air into the right branch a counter-flow ofthe air and the activation mixture originates. The activation mixturedue to the inertia continues its hitherto existing transversecirculating movement up to the moment, when its movement by action ofthe flowing air is stopped and it begins to turn into the oppositesense. These operating cycles may be regularly repeated by means of theregulation. Thus the time of the keeping of the air in the activationmixture is extended, by which the oxygen transition into the activationmixture is increased. Another effect of the counter-flow of the air andthe activation mixture is more effective suspendation of the activatedsludge.

In the distribution channel 5 before the intake to the separation space4 the intensity of aeration can be arranged so that the content ofdissolved oxygen coming to the layer of the fluidized bed filter in theseparation space 4 fully ensures oxyd conditions in the course of thewhole separation process.

A short time of the activation mixture in the separation space duringthe fluidized bed filtration, what is the consequence of the smallvolume in which the separation take place, contributes to the optimumoxide conditions during the separation by the fluidized bed filtrationas well. It is a result of the prismatic form of the separation space 4and of the high filtration speed in the fluidized bed filter.

The described course of the activation biological waste waterpurification with the changing of the oxide and anoxide conditions inthe circulation circuit causes the accumulation of phosphorus from thewaste water in activated sludge. During the following separation of theexcess activated sludge in the separation space the strict oxideconditions prevents the reverse release of the accumulated phosphorusback to the purified water. In such a way a high efficiency of thebiological purification process, even where the removal of thephosphorus from the waste water is concerned, could be achieved. Theclear water is taken away after its passage through the fluidized bedfilter to the removal channels 15.

As it was described, the separation space 4 is connected to thedistributing channel 5 only through one passage 19, at which one or morerectifier(s) 20 of the flow is (are) arranged. This simple solution ofthe inlet of the activation mixture to the separation space 4 is enabledby an intensive recirculation of the activation mixture in thecirculation circuit with its removal at the bottom of the separationspace 4 by the collecting piping 13. The intensity of circulation ofactivation mixture in the circulating circuit influences at the sametime the efficiency of denitrification processes according to theformula mentioned in the first alternative.

From the bottom of the separation space 4 the activated sludge separatedin the separation space 4 during the process of filtration in thefluidized bed is sucked off, and together with the circulatingactivation mixture from the activation distributing channel 5, i.e. fromthe activation process. The intensity of the flow in the lower part ofthe separation space 4 in consequence of the recirculation of theactivation mixture prevents a transfer of perturbations from the aerateddistributing channel 5 to the separation space 4. By this means thestability of the fluidized bed filter in the separation space 4 and ahigh separation efficiency are secured.

The restriction of the interconnection between the activation space andthe separation space to an only passage 19 at the bottom of the tanksignificantly simplifies the construction of the separation space 4. Itenables to use selfcarrying shell structure for construction of theseparation space 4, which consists of only two elements, namely twoseparation walls 3. These walls are attached directly at the bottom ofthe tank and with its other upper end to a not shown supportingstructure.

The system of connecting of more collecting pipings 13 to one pumpingaggregate 41, eventually the installation of more pumping aggregates 41enables keeping of the optimum length of the collecting piping 13 forbig capacities of the waste water purification plants as well, thelength of the separation space of which could reach up to severalhundreds of meters.

The reversible course of the pumping aggregate is used to the purify thecollecting piping by a reverse stream of water.

INDUSTRIAL APPLICABILITY

The method and apparatus according to the present invention is suitableboth for new waste water purification plants construction and forreconstruction of hitherto existing classical waste water purificationplants with individual activation and sedimentation tanks, especiallyfor big capacity plants.

Present invention may consequently be used for a relatively simplereconstruction of said existing waste water purification plants reachingherewith a considerable intensification, namely through increasing theircapacity and their purification efficiency, including phosphorus andnitrogen removal.

We claim:
 1. A method for biological activation waste water purificationcomprisingpumping activated sludge into a circulation circuit, saidcirculation circuit comprising a flow channel and at least onedistribution channel, adding raw waste water to said activated sludge insaid circulation circuit to form an activation mixture, graduallydenitrifying said activation mixture as it flows through saidcirculation circuit, flowing said denitrifying activation mixturethrough said circulation circuit as a plug flow of said activationmixture; aerating said activation mixture to suspend said activatedsludge in said activation mixture while gradually saturating saidactivation mixture with oxygen so as to gradually change thedenitrifying of said activation mixture to the nitrifying of saidactivation mixture as said mixture flows through said circulationcircuit, flowing said activation mixture into a fluidized bed filter toseparate said activation mixture into purified water and activatedsludge, removing said purified water from said circulation circuit,optionally removing a portion of said activated sludge from saidcirculation circuit, pumping said activated sludge into said circulationcircuit, and continuing said process.
 2. The method according to claim1wherein the quantity of said purified water removed from saidcirculation circuit is less than the quantity of said activation mixturecirculating in said circulation circuit.
 3. The method according toclaim 1wherein the amount of dissolved oxygen in said activation mixturesaturated with oxygen is 2 mg of oxygen per one liter of activationmixture.
 4. The method according to claim 1wherein the aerating of saidactivation mixture intensifies as said activation mixture flows throughat least said flow channel of said circulation circuit.
 5. The methodaccording to claim 1wherein the circulation intensity of said activationmixture in said circulation circuit is at least double the circulationintensity of said purified water removed from said circulation circuit.6. The method according to claim 5wherein the circulation intensity ofsaid activation mixture is from 2 to 6 times that of said purifiedwater.
 7. An apparatus for biological activation waste waterpurification comprisinga tank comprising side walls, end walls and abottom surface, at least one basic module positioned on the bottomsurface of said tank and spaced from said side walls and end walls ofsaid tank and defining a flow channel about said module; said basicmodule comprising outside side walls, an end wall and a pair of spacedface walls defining the other end of said module, a pair of partitionswithin said module, each of said partitions extending from one of saidface walls to said end wall of said module and defining a pair ofseparation spaces with the side walls of said basic module, said pair ofpartitions defining a distribution channel therebetween, saiddistribution channel communicating with said flow channel at the openingbetween said spaced face walls, each of said partitions having at leastone opening therein communicating with said separation space and saiddistribution channel, aeration members located in said tank between saidbasic module and said end walls and side walls of said tank, and betweensaid pair of partitions, a baffle plate extending from one of said sidewalls of said tank to said basic module, and collecting means forcollecting activated sludge.
 8. The apparatus for biological activationwaste water purification as defined in claim 7, further comprisingmeansfor conducting at least a portion of said thickened activation mixtureinto said flow channel, an admission means for adding raw waste waterinto said flow channel, means for removing activated sludge from saidseparation space, and a second collecting means for collecting purifiedwater in said separation space, said flow channel and said distributionchannel defining a circulation circuit.
 9. The apparatus as defined inclaim 7wherein said collecting means is proximate said bottom surface ofsaid tank, at least one of said partitions having a smaller upperopening proximate a larger lower opening for communicating between saiddistribution channel and said separation space and forming a droppingresistance against said activation mixture flowing from saiddistribution channel into said at least one separation space.
 10. Theapparatus as defined in claim 7wherein said at least one opening in eachof said partitions communicates with said separation space and saiddistribution channel and extends longitudinally along said partitionsproximate said bottom surface of said tank.
 11. The apparatus as definedin claim 7wherein said collecting means including at least onecollecting main is in said separation space proximate said bottomsurface of said tank, said collecting main having inlets for receivingsaid activated sludge.
 12. The apparatus as defined in claim 11whereinsaid collecting means further comprises a pump communicating with saidcollecting main for removing activated sludge from said separationspace.
 13. The apparatus as defined in claim 7, further comprisingtwo ormore of said basic modules positioned on said bottom of said tank andspaced from said side walls and end walls of said tank.
 14. Theapparatus as defined in claim 13wherein said collecting means includes asump for receiving activated sludge from said collecting main.
 15. Theapparatus as defined in claim 14including means communicating with saidsump and introducing raw waste water into said sump.
 16. The apparatusas defined in claim 13wherein at least one of said basic modules isperpendicular to at least another one of said basic modules within saidtank.
 17. The apparatus as defined in claim 13wherein said basic modulesare arranged perpendicularly and symmetrically about an axis through thecenter of said tank.
 18. The apparatus as defined in claim 17wherein atleast one of said basic modules is parallel to at least one other basicmodule to form a system of basic modules which is symmetrical about anaxis through the center of said tank.
 19. The apparatus as defined inclaim 7wherein a portion of said aeration members proximate said baffleplate have spacing therebetween which is greater than spacing betweensaid aeration members which are further downstream from said baffleplate.
 20. The apparatus as defined in claim 7wherein each of saidseparation spaces provides a pair of inlet openings having a crosssectional area of flow through each of said pair of inlet openings whichis greater than 10% of the top surface area of each of said separationspaces.
 21. The apparatus as defined in claim 7wherein said collectingmeans comprises a centrifugal pump located within a sump.
 22. Theapparatus as defined in claim 7wherein at least one of said openings insaid partitions extends along the length of said partitions, whereinsaid collecting means includes a collecting main extending along saidseparation space.
 23. The apparatus as defined in claim 7wherein each ofsaid partitions comprises a vertical member and a tapered member spacedfrom said vertical member along the length of said partitions.
 24. Theapparatus as defined in claim 23wherein each of said side walls of saidbasic module and each of said partitions form a pair of Y-shapedseparation spaces.
 25. The apparatus as defined in claim 7wherein eachof said partitions defines a plurality of openings.
 26. The apparatus asdefined in claim 7 further comprisingat least one trap in saidseparation space for collecting floated sludge.
 27. The apparatus asdefined in claim 26wherein said at least one trap for floated sludgeextends the length of said separation space, said trap sloping from oneend of said separation space to the other end of said separation space,whereby the floated sludge collected in said trap exits from theseparation space and into the flow channel.
 28. The apparatus as definedin claim 11 further comprisingat least one flow deflector extending fromat least one of said partitions, proximate said opening in saidpartition, and located on the side of said partition proximate saidother partition.
 29. The apparatus as defined in claim 7 furthercomprisinga mixer proximate said baffle plate and having a first andsecond inlet and an outlet, wherein said raw waste water from saidadmissions means enters said first inlet, wherein said activated sludgefrom said pump enters said second inlet, and whereby said raw wastewater and said activation mixture are mixed in said mixer and exitthrough said outlet into the beginning of said flow channel proximatesaid baffle plate.
 30. The apparatus as defined in claim 12wherein saidcollecting means further comprises a submersible reversing electricmotor for driving said pump.
 31. The apparatus as defined in claim 30further comprisingguiding bars extending from the bottom of said tankbottom, said pump having a runner, said submersible reversing electricmotor and said runner slidably mounted on said guiding bars.
 32. Theapparatus as defined in claim 30wherein said pump is connected with atleast two collecting mains.
 33. The apparatus as defined in claim 11further comprisingan air pressure supply, a plurality of aeration meansin said flow channel and said distribution channel and in communicationwith said air pressure supply, for aerating said activation mixture. 34.The apparatus as defined in claim 33wherein said aeration means compriseaeration hoses having a plurality of spaced openings therein for passageof the air therethrough, said aeration hoses extending along the bottomof said tank.
 35. An apparatus for biological activation waste waterpurification comprisinga tank comprising side walls, end walls and abottom surface, a modified module positioned on the bottom surface ofsaid tank and spaced from said side walls and end walls of said tank anddefining a circumferential flow channel about said module, said modifiedmodule comprising a first side wall, a second side wall, and end wallsdefining a separation space therein, said first side wall and one ofsaid side walls of said tank defining a distribution channeltherebetween, said distribution channel comprising one length of saidcircumferential flow channel and communicating with said circumferentialflow channel at one end of said first side wall, said first side wallhaving at least one opening therein communicating with said separationspace and said distribution channel, aeration means located in said tankbetween said modified module and said end walls and side walls of saidtank, a baffle plate extending from one of said side walls of said tankto said modified module, and collecting means for collecting activatedsludge from said separation space.